Lock cylinders that can be rekeyed without removal of the cylinder plug are known. For example, U.S. Pat. No. 8,033,150 describes a rekeyable lock cylinder. These types of locks are highly beneficial to consumers because the locks can be easily rekeyed without use of a locksmith.
Although the plug cylinder should freely rotate when an authorized key is inserted into the keyway, the lock cylinder should be configured to resist rotation of the plug when torque is applied by an unauthorized key (or other object). A high amount of torque resistance for the lock cylinder is key to reducing forced entry. Therefore, there is a need for a rekeyable lock with enhanced torque resistance.
According to one aspect, this disclosure provides a rekeyable lock cylinder with a cylinder body and a plug assembly. The cylinder body defines a longitudinal axis and includes a groove. The plug assembly is disposed in the cylinder body and is rotatable about the longitudinal axis. The lock cylinder includes a plurality of key followers and a corresponding plurality of racks disposed in the plug assembly. At least one of the plurality of racks is selectively disengageable from at least one of the plurality of key followers responsive to application of a force by an object inserted into the rekeyable lock cylinder to facilitate rekeying to a new key. The lock cylinder includes means for blocking rotation of the plug assembly with respect to the cylinder body to prevent unlocking of the rekeyable lock cylinder with an unauthorized object. In some embodiments, the blocking means is configured such that torqueing the plug assembly with an unauthorized object applies force to the blocking means without translating such force to the plurality of racks. This type of arrangement enhances torque resistance of the lock cylinder.
In some embodiments, the blocking means includes a locking bar movable transversely with respect to the longitudinal axis between a locked position into the groove of the cylinder body and an unlocked position out of the groove of the cylinder body. For example, the locking bar could include a surface that engages a surface of the groove when in the locked position. In some illustrative embodiments, the respective surfaces of the locking bar and groove that engage when the locking bar is in the locked position are in approximately parallel planes. Depending on the circumstances, the surface of the locking bar that engages the groove in the cylinder body when the locking bar is in the locked position is not a ramped surface. For example, the surfaces could be flat with respect to each other. In some cases, the edge of the locking bar is substantially squared off, such as having an approximately rectangular cross-section.
In some embodiments, there are one or more biasing members urging the locking bar towards the plurality of racks. With this arrangement, the biasing members urge the locking bar out of the groove in the cylinder body when an authorized key is inserted into the keyway. In some illustrative embodiments, a spring force of the biasing member is less than a spring force of the spring-loaded key followers. As such, the spring-loaded key followers will overcome the spring force of the biasing member to lock the lock cylinder when a key is not inserted into the keyway.
Additional features and advantages of the disclosure will become apparent to those skilled in the art upon consideration of the following detailed descriptions exemplifying the best mode of carrying out the disclosure as presently perceived.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates an embodiment of the invention in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.